1. Field of the Invention
The present invention generally relates to an improved filtering system of the horizontal belt type for dehydrating slurries.
2. State of the Art
Conventional horizontal belt vacuum filters include two drums which are horizontally disposed and rotatable about their horizontal axes. The two drums are rotatably affixed to a frame. An endless drainage belt is disposed around the two drums to define a substantially horizontal drainage surface on the upper run of the belt between the lower edges of the two drums. The drainage belt is flexible so that as the drums are rotated the belt can continuously travel around the drums. The drainage belt is perforated so that liquid on the upper run can flow through the perforations. A drive means is coupled to one of the drums to cause it to rotate, thereby causing rotation of the drainage belt and the other drum. A continuous belt of filter media is disposed around the drainage belt to be carried by the upper run, and a plurality of rollers is located below the drums to carry the filter media.
Feed means is disposed above the horizontal drainage surface near one of the drums. The feed means introduces slurry atop the filter media on the horizontal drainage surface. A vacuum pan is disposed below the horizontal drainage surface to apply vacuum to the slurry thereon to dehydrate the slurry.
In practice it is often necessary to lower the vacuum pan away from the horizontal drainage surface for cleaning or repair. A patented system for lowering the vacuum pan is taught in U.S. Pat. No. 4,080,298.
In some conventional horizontal vacuum systems a worker has to crawl between the belts to gain access to the vacuum pan. Thus it is necessary for the space between the upper and lower runs of the belt to be large in such systems. Two conventional ways of enlarging the space between the runs are to either make the drums large or to utilize small spreader rollers beneath the drums to lower the lower belt run. There are significant disadvantages to either of these approaches. For example, if the drums are large, expensive machinery is required to drive the drums. If spreader rollers are utilized it is, of course, necessary for the belt to pass over the small rollers. Thus the belt is required to flex considerably thus contributing to rapid wear and deterioration.